Various display devices have been actively researched and developed in recent years. In particular, organic electroluminescence (EL) devices attract much attention because they can emit light at a high luminance with low voltage applied. For example, a light-emitting device comprising organic thin layers provided by vapor-depositing organic compounds is disclosed in Applied Physics Letters, Vol. 51, page 913 (1987). This light-emitting device has a structure where an electron-transporting material of tris(8-hydroxyquinolinato) aluminum complex (Alq) and a hole-transporting material of an amine compound are disposed between electrodes as a laminate, thereby exhibiting more excellent light-emitting properties than those of conventional light-emitting devices having a single-layer structure.
Active research and development have been made to apply organic EL devices to full-color displays in recent years. To provide high-performance, full-color displays, light-emitting properties should be improved for each of blue, green and red colors. For instance, blue-color, light-emitting devices are disadvantageous in color purity, durability, light-emitting luminance and light-emitting efficiency, and thus their improvement is desired. To solve these problems, devices comprising aromatic condensed-ring compounds were investigated (JP 11-12205 A, etc.), but there is still a problem that such light-emitting devices are low in light-emitting efficiency, failing to emit blue light with high color purity. In addition, improvement is desired in organic EL devices, too.